Ionic exchange operations



Jan 7 F. N. RAWLINGSA En; 2,413,784

ION-IG EXCHANGE OPERATIONS 4 sheets-sheet Original Filed Jan. 14, 1942 lmwvl toi tkmtmhk lunttl Bittbk RAT INVENTORS y FRANKLIN IY. Ra w1. mas Lows of Gear-nov 5 Y ATTORNEY 7, 1947- F. N. RAwLlNGs nm. 2,413,784 l Ionic ExcHANGE OPERATIONS l original Filed Jan. 14,194.2l 4 sneets'fsneet :s

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F. N. RAwLlNGsEi-AL 2,413,784

IoNIc EXCHANGE oERATIoNs j C T/oN ExcH/INGER SM1-10N SnruRfvrlo/y PHASE) ATTORNEY -action products.

Patented Jan. 7, 1947 T OFFICE IONIC EXCHANGE OPERATIONS Franklin N. Rawlings,

Louis deGeofroy,

Westport, Conn., and New York, N. Y., assignors to The Don- Company, New York, N. Y., a corporation of Delaware Original application Jan 426,718. Divided and uary 14, 1942, Serial No. this application vDecember 4, 1943, Serial N0. 512,894

3 Claims.

l This is a division of my Serial No. 426,718, filed January .14, 1942.

patent application The bed ready for operation in the next cycle, while parent application relates broadly to ionic exchange operation, and specically to a manner of regenerating a bed of cation exchanger material which operates in the H-ion cycle and requires H2SO4 as a regenerant solution. The parent application covers the procedure of treating the exhausted or saturated bed of exchanger material with an auxiliary regenerant solution prior to applying the HzSOi regeneration. 'I'his auxiliary step is for the purpose of displacing from the saturated bed those cations (for instance Ca) that are precipitable insofar as they would form with the H2804 regenerant solution insoluble re- In this Way, the precipitable ions are replaced with the molar equivalent of cations that are non-precipitable (such as Na and K) insofar as they will form with the HzSO-l regenerant solution soluble reaction products. Ihis procedure includingthe auxiliary treatment step makes it possible to avoid undesirable precipitations in the exchanger bed coincident with the msm regenerations.

Reference is also had to a copending patent application Ser. No. 376,717, led January. 31,

` 1941, by Franklin N. Rawlings, who is one of the co-inventors in the present application. The copending application describes an ionic purication process for sugar bearing liquids or sugar juices,

in which the juice is subjected rst to a cation ex` change, and then to an anion treatment step.

In describing a complete operating cycle this copending patentapplication recommends for thev regeneration of a 'synthetic resinous exchanger bed an H2SO4 solution of a concentration on the order of 5%.

The present divisional application covers the procedure of treating a solution containing both the precipitable and the non-precipitable `kind of cation, first in one bed to which the precipitable kind becomes xed in exchange for non-precipitable cations. As a result of this auxiliary treatment step, eiliuentsolution leaving the rst bed contains only non-precipitable cations. It is then treated in a second bed where H-ion exchange may take place without the danger of sulphate precipitation in the bed. In this cipitable cations are removed from the' solution in a separate step or bed which isolates the undesirable cations, and which auxiliary bed is regenerable with an inexpensive regenerant solution such as NaCl. By the auxiliary regeneration with NaCl the isolated cations such as Ca are replaced with non-precipitable Na rendering'the auxiliary way. the prematerial that is of organic the Ca leaves the system in the spent auxiliary regenerant liquor.

There now follows an exact copy of the parent application:

This invention relates to improvements in the conduct of ionic exchange operations. More speciiically, this relates to the use ofkcation exchangers operating in the hydrogen ion cycle. That is to say, it relates to the treatment of solutions from which cations are to be removed by means of a cation exchanger in exchange for H-ion, which exchangers must be regenerated after their exchange capacity has been exhausted and they have become saturated with cations from the solution being treated.

An ionic exchanger is usually represented in the form of a, unit or cell containing a bed of the exchanger material proper which is usually granular. An exchanger has the ability to absorb from the solution an ion of an ionized solute and to give off into the solution in exchange anion of another kind even though of like electric charge. Therefore, cation exchangers as a class exchange positively charged ions, whereas anion exchangers as a class exchange negatively charged ions.

vAs the solution is passed through and contacted with the ion exchanger bed, the direct exchange of respective ions between the solution and the exchanger continues until the exchanger is .saturated with the ions being removed from the solution and its exchange capacity thus exhausted. The exchange capacity cari then be restored by treatment of the exchanger with a suitable regenerant solution. The saturation on the one hand, and the regeneration on the other hand, represent the main phases of the operating cycle of an exchanger, whereby the exchanger may be used over and over again. The chemical reactions involved in the operating cycle are reversible'equilibrium reactions.

More particularly the invention has to do with such beds that make use of granular exchanger nature and acid resistant to the extent that it Will remain bodily stable in the presence of certain strong acids (for instance,HCl and H2SO4) by means of which they are to be regenerated.

' of exchangers now newly called organolites in distinction from the inorganic base exchangers 'I'his belongs to a class anion exchangers,

environnient of this invention. The essence cf the method of purifying the juice or sugar bearing solution through ionic exchange treatment is that the juice is sent through a sequence of cation and with the net result that dissolved salts in the juice are removed in exchange for the molar equivalent of in the treatment of sugar juice will be described more completely further below.

A cation exchanger of the organolite type, being of organic nature and acid resistant, can be regenerated with one of the commonly known.

tions from which the cation exchanger has re-` moved and collected cations among which are some that form with the regenerant sulphuric acid a poorly soluble or insoluble sulphate. Such a precipitate or deposit or coating upon the granules of the exchanger material presents an obstacle to the proper exchange function of the exchanger, and greatly reduces its eiectiveness. In the specificv case-of ionic exchange purification treatment of some sugar bearing juices or syrups, calcium may be present in them to an objectionable degree and under ordinary conditions of exchange treatment, may collect in the exchanger to an extent that will cause undue quantities of insoluble calcium sulphate precipitate to deposit upon the exchanger material during regeneration with HzSO4.

The object of this invention is to overcome this diiculty and to propose a process which makes possible the .use ,of sulphuric acid as an inexpensive regenerant, without the occurrence of the objectionable precpitaes from the H2804 reaction with such trouble causingcations as calcium or others.

The invention proposes to isolate the undesirable or precipitate forming cations by means of selective or preferential ionic exchange, prior to aplying HzSOi as a regenerant to an exhausted cation exchanger. It is proposed to utilize certain selective or preferential exchange characteristics of the exchanger material. Such characteristics are in the nature of a certain order of exchange affinity possessed by the exchanger with respect to a variety of ionic substances present in the solution. that is being treated by the exchanger. In

other words, the cations in the solution form a sequence or series as regards their exchange afiinity with respect to the exchanger. I But it should also be understood that this nautral se: quence is modifiable in effect by a deliberate change of the concentrations of the respective ions in the solution. That is to say, the natural preference of the exchanger forone cation can be overcome or suppressed by another cation even though of weaker alnity with respect to the exchanger, provided it is allowed to act upon the exchanger in a sufficiently strong concentration. The aiiinity characteristics of an exchange mayI be explained by way of general example as follows: Y

Assuming a solution contains a mixture of two salts A and 3" as solutes, and that the exchanger llas a preference or aillnity for the cation pure and evaporable water. The mechanism of this ionic substitution of the salt "A over the cation of the sait B, if

the solution is passed through the exchanger bed that has been freshly regenerated, that bed wil1 absorb all the cations from both the salts A and B indiscriminately in exchange for its own cations until it is substantially saturated with absorbed cations, that is until its exchange capacity is exhausted. This period is herein called the, primary period of' ionic exchange of the exchanger. If the sa-me fresh solution is continued to be passed through the `saturated exchanger, the latter will begin to manifest its selective characteristics by releasing the previously absorbed cation of the salt B in exchange for preferred cations of the salt A" in the solution. This will continue until the exchanger is saturated with only the preferred cations of the salt A. Cation exchangers such as herein contemplated have a. preferential action for I'the alkaline earths such as Ca and Mg over the alkaline metals such as represented :by K and Na, all of which cations are found to -be present in varying degrees in sugar juice.

That is to' say, it has been found that ionic exchange materials operating in the hydrogen ion I pacity, it will discontinue removing sodium and potassium from the solution and begin to exchange the already absorbed sodium and potassium for calcium in the incoming juice, and continue in this preferential exchange until substantially all of the sodium and potassium it has previously absorbed is replaced by calcium, whereby finally the exchanger bed is left-Casaturated. In this secondary or preferential exchange reaction, the exchanger is, so to speak, operating in the sodium and potassium cycle instead of in the former hydrogen ion cycle.

Alior the same reason, if an exchanger is assumed to have been saturated with a series of cations of different amnities, it is possible to displace from the exchanger some of these ions, which have a weaker afnity to the exchanger than the displacing ion. In this way all ions can be displaced excepting the ion or ions having equal or greater affinity to the exchanger than the displacing ion. i

Forexampl if a cation exchanger were saturated with Ca and K-ions, one could treat the exchanger with a Cach-solution and thereby displace thev K-ion with Ca-ion because of the 'natural preference of the exchanger for Ca. The sotration, when the Ca saturated exchanger is conv tacted with the KCl solution, all the Ca-ion in turn may be replaced with K-ion, whereby then the exchanger will be left all K-saturated.

In order to attain the object of this invention, the cation exchanger is allowed to become saturated with a variety of cations from a solution, including those ions that are potentially capable of forming undesirable precipitates on the exvchangermaterial, when in reaction with HzSOi during the subsequent regeneration of the exchanger with that acid. However. according to the invention, before applying this regenerant acid, the exchanger is rst subjected to an ionic displacement operation by way of treating it with an auxiliary solution, whereby the precipitate forming ions are replaced with the molar equivalent of ions that will not form H2504 reaction products as precipitates. For example, a calcium containing cation exchanger may be treated with NaCl solution of suiiicient strength until all the Ca in the exchanger yhas been replaced with Na, whereupon it may be regenerated with H2SO4 in the hydrogen ion cycle, whereby soluble sodium sulphate is produced. The spent regenerant liquor thus passes from the exchanger without leaving behind any harmful sulphate deposits.

Inasmuch as the ionic purication treatment of sugar juices is herein chosen as an example embodying this invention, and so that the environment of the invention thus embodied may be clearly understood, there now follows a brief description of the chemical exchange mechanism whereby ionic impurities or dissolved salts in the sugar juice are subtracted therefrom and replaced with the molar equivalent of pure and evaporable water.

In extracting non-sugars and especially salts from sugar-making juice or syrup, two main types of exchanger beds are used. One is called the cation exchanger bed that is characterized by its .use of exchanger material that operates on the hydrogen-ion cycle and is adapted to collect from the juice plus or positively charged ions represented generally by calcium,vmagnesium, sodium and potassium. That is, as juice is supplied to the cation exchanger bed (or cell that contains the bed) so as to ow through it and out therefrom, cations of the juice exchange themselves for the hydrogen ions of the exchanger until the exchanger bed becomes exhausted of its exe change capacity and so saturated with vthose cations that it ceases substantially to exercise further hydrogen exchange activity. Thereupon the cation bed must be regenerated by contact with a regenerant in the form of an ionized strong acid such as hydrochloric or:sulphuric acids. During regeneration, the reverse process takes place in the exchanger, namely, the residual cations exchange with hydrogen ions of the acid regenerant so that the cations iiow from the bed until the bed is recharged with hydrogen ions.

Juice that passes from the cation bed has had its impurity contentof basic ions substantially removed, but it yet contains chlorides, sulphates and other such negative ionic impurities. So the juice, substantially rid of its positive ionic or cation impurities that have been left in the exchanger, is passed to and through an anion exleft in the exchanger. Thusthe acid or positive ions oi the juice are reA oved from it while passing through a cation exchanger bed and the negative or acid forming ions are removed from it while passing through changer bed. y

This cation and will be more lowing example: A v Sugar ,'luicev containing KCl goes in the cation bed, in, passing through which KCl and.l HX (X being the structure ofthe cation exchanger) of the bed become IQ! and HC1. ows from the cation bed with the juice is then passed through the incoming HC1 and the OHY (-Y being the structure of theanion exchanger of become ClY and water, so that sugar juice flows from the anion bed minus its KCl.

During the regeneration in the cation bed, if HC1 is-used as with the residual KX to form HX and KCl, the latter iiowing from the cation bed leaving the bed regenerated. If H2804 be usedas regenerant acid, the spent regenerant liquor would accordingly contain the K as K2SO4 which is a soluble sulphate. During regeneration of the anion bed, the incoming regenerant NaOH reacts with the ClY to `form OHY and NaCl, which latter flows from the bed, leaving the anion bed regenerated.

Again, the problem lies with regeneration of the cation exchanger in view of the possibility of sulphate deposits on the exchanger material. Sulphuric acid being fromv one-third to onefourth the price of hydrochloric acid, it is preferable naturally, to use sulphuric acid. Cane juice, for instance, contains suiiicient calcium so that when sulphuricV acid is`used for regeneration, calcium sulphate is found or yielded in such concentration as to precipitateinthe changer bed or cell that operateson a hydroxyl,

cycle. In passing through the anion bed, the chloride and sulphate, etc., ions of the juice are exchanged for the hydroxyl ions of the bed until theanion bed becomes saturated with chlorides and sulphates, etc. Thereupon the saturated anion bed must be regenerated by contact with some ionized alkali hydroxide or carbonate, espe-'- cially sodium hydroxide. or carbonate. During regeneration, the reverse process takes place, namely, the residual chloride and sulphate, etc., ions in the bed exchange with hydroxyl ions of the basic regenerant so that the negative ions or anions `iiow from the bed untilthe anion bed is recharged with hydoxyl ions. In passing through the anion bed, the juice is substantially rid of its e ingl an exhausted action exchanger .bed during regeneration. 'Ihis precipitation tends to block mechanically the normal exchange function'of the exchanger bed, causing a marked reduction in the exchange capacity of the regenerated cation exchanger.

This invention proposes, therefore, a method used in the regeneration of those exchangers. The remedy according to this invention lies in subjecting the exchanger to an intermediate treatment or conditioning step whereby the Ca or precipitate forming cations are displaced from the exhausted exchanger by actions whose potential sulphates will remain dissolved in `the spent regenerant liquor. This comprisestreatexchanger bed with a suiiiciently strong solution of common salt (or its equivalent) to replacev the Ca of the vexchanger bed with Na from the salt. This auxiliary treatment step leaves the exhausted exchanger saturated mainly with Na 'and K, such being `the representatives of the alkali metals and the alkaline earths respectively in the sugar juice. The exhausted cation exchanger bed thus conditioned or pre-regenerated in the Na cycle, can be safely regenerated in the H-ion cycle, that is, with sulphuric acid. Due to the absence of Ca in the exchanger, no insoluble form. The sulphates of Na and K that will form, are soluble and thus harmless to the proper functioning of the operating cycle of the exchanger negative or saltforming ions since they have been 75 bed.

a subsequent anion exanion exchange mechanism precisely understood from the fol-` 'rhe HC1 that v anion bed and, in so doing, the

the anion bedr intial V content of l a, regenerant, that acid reacts' calcium sulphate will of any such cations collected 7 According to one embodiment, or mode of operation of this invention, the total exchange operating cycle is performed in two exchanger stages. That is to say, the Juice is pamed through a rst cation exchanger stage operating in the auxiliary or Na regeneration cycle where all the Ca from the juice is selectively collected by, and then displaced from exchanger, whereupon the thus conditioned juice is passed through a seci exchange stage operating in the H-ion regeneration cycle, where cations are removed that do not form insoluble Rasoi-reaction products.

In this connection it is to be remembered from `the foregoing, that all the Ca from the juice can be selectively collected in the first exchanger stage because the cation exchangers have a much greater affinity for the calcium ions than for the sodium or potassium ions. That is to say, if the exchanger becomes first exhausted with a variety in it, then if additional juice is contacted with it, the exchanger will, by reason of its preference, remove the Ca from the additionally flowingjuica-yielding in exchange an equivalent quantity of sodium or 'potassium which, it had previously removed and collected.

If a sulcient proportion of the cation exchanger (representing the rstexchanger stage) is left in the circuit after the exchanger has become exhausted with respect to hydrogen ion exchange, and if this is followed by other cation exchanger not exhausted with respect to hydrogen ion exchange (this is the second exchanger stage) the exhausted exchanger stage will selectively take up all of the Ca while the non-exhausted exchanger stage will take up the K and Na. The first exchanger stage having become all Ca saturated, can be treated with a solution of sodium chloride (NaCl) of sufdcient concentration in order to substantially remove the Ca from the exchanger by displacing it with Na. After washing out the residual NaCl from the bed, the exchanger can again be used to take up more Ca from the juice, and the Ca-free juice then vbe passed through second stage exchanger material active in the H-ion cycle in order to remove the K and Na. The exhausted second stage exchanger bed containing the K and Na is regenerated with HzSOs because it doesnt contain precipitate forming impurities, and after washing out the residual acid from the bed, this second` stage exchanger can' again be used to effect Na-and K-removal, in sequence to the first stage exchangerA bed or beds employed to remove the Ca alone from the juice.

In the course of a complete operating cycle, each of these exchangers, if exhausted, is to have the residual juice therein displaced from the exchanger bed with wash water, and if deposits have collected on the exchanger granules they are toy be washed out, before the exchanger if subjected to contact with the regenerant solution, Again, if regeneration is completed, the residual regenerant is to be displaced and washed out from the exchanger with water, before the exchanger is again contacted with the juice, In this way undesirable reactions between ionic constituents of the juice and regenerant solution in the exchanger bed can be avoided and the exchanger be kept in regular cyclic operation with substantially undiminished efliciency.

The exhaustion or saturation of a fresh exchanger bed with the solution flowing downwardly therethrough proceeds in continuous fashion from the top to the bottom of the ex changer body. Hence, there exists, yapproximately speaking, a dividing line or relatively narrow zone of transition between the upper exhausted or saturated portion of the exchanger body and the lower non-exhausted or non-saturated portion of that body. This dividing line or zone keeps shifting downwardly through the exchanger body as the vcontinuously through-flowing solution leaves an increasing exhausted exchanger portion behind as it advances through a correspondingly decreasingv portion of non-exhausted or still active exchanger. However, as

the dividing line is not necessarily a `sharp one, l

there will be noticed a slowing down of the exchange intensity as the break-through point of the exchanger is being approached. This is a warning that the fresh or regenerated exchanger should be substituted for the one nearing saturation. The regeneration of a bed proceeds in asimilar manner through' the bed. Y

One of a variety of organic cation exchangers considered suitable for the present purpose is of the resinous type such as exemplied in the United States patent to Holmes No. 2,191,853, where the exchanger is described as a synthetic resin of the polyhydric phenol formaldehyde type which is sulphited to adegree such that its sulpur content is not less than 2.4%. An organic anion exchanger considered suitable for the present purpose is also exemplified in the United States patent to Adams and Holmes No. 2,151,883, describing the exchanger as an insoluble .resin-like product -obtained by the reaction of formaldehyde with an aromatic amine. Exchangers of the type contemplated for use inv connection with the present invention, are substantially stable in the presence of acids and alkalis.

- Other suitable organolite exchangers are: The cation exchanger produced by the Resinous Products Corp. of Philadelphia under the name or identification of Amberlite IR.1, and the anion exchanger Amberlite IRA from the same source. These areexchanger materials of synthetic resinous nature, and more specifically materials which are prepared by the condensation of a dissolved organic chemical of a group comprising sulfonated phenols and aromatic amines, with an aldehyde.

The invention possesses other objects and fea- Y tures of advantage, some of which, with the foregoing, will be set forth in the following description. In the following description and in the claims, parts will be identified by specific names for convenience, but they are intended to beas generic in their application to similar parts as the art will permit. In the accompanying drawings there have been illustrated the best embodiments vof the invention known to nie, but such embodiments are to be reg'arded as typical only of other possible embodiments, and the invention is not to be limited thereto.

The novel features considered characteristic of my invention are set forth with purticularity in the appended claims. The invention itself, however, both as to its organization and its method of operation,'together with additional objects and advantages thereof, will best be understood from the following description of a specic embodiment when read in connection with the accompanying drawings in which:

Fig. 1 is a diagrammatic illustration of the cyclic operation of the cation exchanger operating as a single exchanger stage, in which the of the resinous type and is f Lleaving Na and K intermediate or in the K cycle.

rig. 2 is similar to Fig; 1, except that the intermediate regeneration is in the Na-cycle,` to be removed from :the ex-` changer by H-ion cycle'regeneration.A

lFig. 3 illustrates the two-stage method in which the intermediate or auxiliary regeneration is performed in the Na cycle in the iirst exchanger stage, andthe H-ion regeneration (using I-IaSO4) is performed in the second exchanger stage.

Figs. 4 and 5 illustrate the mode of operation or operating cycle shown in Fig. 3, by representing an intermediate conditionjinthe operating phases of the two cation exchanger beds, namely, when the two-beds are partly exhausted during the saturation phase (see Fig. 4),

In practicing the invention according to Fig. 1, the juice containing as chlorides Ca as well as K (as representatives of the alkali metals and of the alkaline earths respectively) is started owing through a cation exchanger bed which is freshly regenerated in the H-ion cycle, a condition herein designated as Ci.

tion:

l Sugar juices and Sugariuices and H-J i-H Syrups containing X=Ca syrups contain- CaCliand2KCl ingiHCl In due course the H-ion exchange capacity of the exchanger will become exhausted, as Ca and K from the juice accumulate therein in exchange for the, available H-ion, this exchange reaction resulting in the formation of 4HCl (hydrochloric acid) in the juice. I'he exhausted or saturated condition of the exchanger at the end of the .saturation phase is designated as C2. AThe juice that is having its Ca and K removed by the exchanger, having thus becomes acidified in the process, is then passed on to and through an anion exchange treatment station Where the negative ion of the acid is replaced with OH-ion which combines with the positive or H-ion pure water (HOI-I or H2O). The dissolved salts or impurities (CaClz and 2KC1) originally present This means that the exchanger is treated with KCl solution of suicient strength to displace and replace the Ca, the initial condition of the exchanger during this treatment phase being designated as Cs. This-is continued until all the Ca in The saturation of this bed by the through-cwing juice with Ca and K proceeds according to the following equaof the acid to form auxiliary regeneration step eration proper with H2SO4-of suitable concentration, that is, regeneration in the H-ion cycle, as represented in the following equation:

K H K-x-x maso H-x-H zmso That is to say, Hzsoi is started flowing through and partly'- v regenerated in the regeneration phase (see Fig. 5)

' absence of calcium the K-saturated'exchanger bed, andv the condition of the bed at the beginning of this phase is designated as C5. This continues until all K-ion are replaced with H-ion, the K being yielded'by the exchanger and' therefore present in the spent regenerant liquor as K280i, that is, potassium sulphate that is changer can be re-used in the initial condition C1 of the saturation phase, that is, at the beginning of the total operating cycle. Because ofthe sulphate deposits on the ex-` changer granules, this cycle can be maintained repetitively in smooth operation.

However, sodium chloride (NaCl) is a suitable and inexpensive auxiliary regenerant substance, and its use as such is embodied in the two ymethods of operation'accoiding to Fig. 2 Vand Fig. 3

respectively.

In Fig. 2, the saturation phase of the total operating cycle comprises starting the iiow of juice containing Ca `and K as chlorides, through a suitable cation exchanger which has been freshly regenerated in the H-ion cycle and therefore has positive or H-ions available for exchange.' This condition of the exchanger is designated as is continued the exchange C7. As the 'ow of juice reaction between the available H-ion in the exchanger withjthe Ca and K-ion in the juice proceeds according to the Equation 1 as above. If

lthis is continued until the available H-icns in the exchangerhas been replaced with-K, placing the exchanger in the condition designated as C4. Thus the exchanger is .all K-saturated, as the Ca is contained in the spent liquor as CaClz.

The exchanger can now be subjected to regen-l ldition Cs in Whichit is all Ca- 4 The juice leaving the exchanger is thus rendered the exchanger have been replaced with Ca and K-ion, the exchanger will have assumed the conand K-saturated.

free of Ca and K, although spondingly acidiied since it bined Ca and K equivalent in it becomes correcontains the comhydrochloric acid.

The thus acidiiied juice is passed to an anion y treatment station (not shownin the drawings) where the acid is converted into the molar equivalent of H2O, as was described in connection with the removal of cations from the juice during the saturation phase in Fig. 1. l

The exchanger is vthen subjected to intermediate vor auxiliary regeneration, namely, regeneration in the Na-cycle, with NaCl solution as the auxiliary regenerant. The condition of the exchanger bed at the beginning of this intermediate phase is designated as C9, andit proceeds according to equation'- v(s) Na This is continued untilall lthe Ca-ion in the exchanger will have been replaced with sodium ion. The condition of the bed atthe end of this regeneration phase is designated as Cip.

Then begins the 'regeneration proper of the exchanger in the H-ion cycle by means of HzSOi, which proceeds according to equationsoluble. Thereupon the exning of this iinal regeneration The condition of the exchanger at the beginphase is designated as Cn. The exchange according to Equation is continued until all Na and K-ion in the exchanger have been replaced with H-ion from the acid, when the exchanger bed will have reached its fully regenerated condition designated as C12. Consequently, the displaced Na and K are present in the spent regenerant liquor as N2SO4 and K2SO4. The exchanger bed is then ready to be re-used at the beginning of the operating cycle Where its condition was designated as C1.

In Fig. 3 the invention is embodied in a twostage operating system, permitting the auxiliary (Na-cycle) regeneration to be performed in the first exchanger stage, while the H-ion regeneration (using H2804) is performed in the second exchanger` stage. That is to say, the juice is passed sequentially through both stages, while each stage is regenerated in its own respective cycle. In the first stage the juice is conditioned,

. by virtue of selective Ca-removal, for H-ion exchange treatment in the second stage period. Because of the conditioning action of the iirst stage, the cations present in the juice entering into the H-ion exchange phase, are of such a kind that their H2504 reaction products will not form objectionable precipitates during H-ion regeneration of the second stage exchanger. bed.

For this purpose, the first stage exchanger bed may be assumed to have been regenerated in the Na-cycle, so that it is saturated with Na-ion when juice containing Ca and K as chlorides is started flowing through it at the beginning of the operating cycle. The condition of the bed, when the juice begins to flow into it, is designated as C13.

Since the exchanger has a preference for Ca over Na, it will absorb the Ca` from the juice, releasing Na instead into the juice, rendering the juice thus treated free oi.' Ca but leaving in it Na and K according to the following exchangereaction equation- Sugar Solution Na -Na -v Susa olutlon -l- X=Cn KCl 6c 208C): l

r S KCl & 4NaC Na a .cycle regeneration which proceeds according to equation- Ca l Na That is to say, NaCl solution of suiiicient strength is started to be passed through the bed then in a condition designated'as C15. The NaCl solution is of a strength suiiicient to suppress the initial Ca preference vof the exchanger and to eiIect displacement of the Ca-ion therefrom. Consequently, when all the Ca has been replaced with Na., the exchanger is all Ca-saturated and in a condition herein designated as Cie. The displaced Ca is present as CaClz in the spent liquor flowing from the bed.

Meanwhile the juice having been freed of Ca, 'but containing 'Nal and K. is passed through the second cation exchanger. bed for the purpose of 12 exchanging H-i'on from the exchanger against the Na and K-ion from the juice.

At the beginning of this saturation phase the condition of the exchanger is designated as Cn. The saturation proceeds according to the equation- 8 No izgar solution l Sugar solution NaCl & 2K0] H-X-H K-X-K -i-y containing (from 6) Iii Na 21101 The Na and K saturation oi the exchanger according to Equation 8 proceeds by continuing to iiow juice through the exchanger until substantially all available H-ion therein have been ex. changed against the Na and K-ion from the juice. when the exchanger will have become Na and K-saturated, a. condition herein designated as Cia. 'I'he juice treated vduring this saturation phase emerges freeof Na and K, although containing the combined Na and K equivalent in hydrochloric acid. The thus acidied juice is then passed on for treatment in an anion exchange station (not shown in the drawings) where the acid in the juice is converted to pure water, as above explained in connection with the operation according to Fig. 2 and Fig., 3.-

The second stage exchanger bed can now be regenerated in the H-ion cycle by means of treating it with H2S04 of suitable concentration. The condition of the bed, when the regenerant acid starts entering it, is designated as Cin. The exchange whereby the Na and K in the exchanger are replaced with H-ion from the acid, proceeds according to equation- (o) Ne 11 x-X-K 2H=so4 H-x-H Naso. xiao.

This is continued until all the N a and K will have been replaced with H-ion; when the exchanger will have reached its regenerated condition herein designated as C. Spent regenerant liquor flows from the exchanger, containing the displaced Na and K as NaaSO4 and K130i, both -of which are -soluble, and therefore harmless,

since they leave no objectionable and obstructive deposits upon the exchanger material, whereby its exchange effectiveness might be interfered with. The thus regenerated exchanger can then be re-used at the beginning of the H-ion regen--l eration cycle, where the condition of the bed is identified as Cio.

Another way of illustrating the method of isoiating Ca from the juice according to Equations 6, 7, 8, 9 is shown in the diagrams of Figs. 4 and 5. Instead of showing the initial and nnal condition of the exchanger beds (as shown in Fig. 3), Figs. 4 and 5 show an intermediate condition of the beds in their saturation and regeneration phase respectively.

Fig. 4 shows the saturation of the two cation exchanger stages. The juicewhich is assumed to contain appreciable amounts of Ca and K in 'the form of chlorides and as representing the alkali metals and the alkaline earths respectively, is shown to have passed through the first cation exchanger stage long enough to have placed it into the condition designated as Cn. This bed was originally regenerated in the Na cycle whereby it has adsorbed N a-ion, but in the condition Cn the upper portion a thereof has become saturated withv Ca in exchange for Na-ion because of the preference or affinity of the exchanger for i3 Ca. while the lower portion b of the bed still contains available Na-ion. Consequently, the juice leaving the bed is free of Ca but contains Na and K.

The juice then enters the second cation exchanger stage or bed the intermediate condition of which is designated as C22. Originally this bed was regenerated in the H-ion cycle whereby it has adsorbed H-ion available for exchange, but in the intermediate condition C22 the upper portion c of the bed is saturated with Na and K-ion in exchange for H-ion yielded, while the lower portion d still contains H-ion available for exchange.` The juice leaving the bed is free of Ca, K and Na, but contains the molar equivalent of these ions in hydrochloric acid formed as the net result of this cation exchange. 'I'he hydrochloric acid in turn can be replaced with its molar equivalent of H2O by means of treating the juice in a subsequent anion exchanger station (not shown).

Fig. 5- shows the regeneration of the two cation exchanger stages or beds after the same have become exhausted due to the saturation of the irst bed with Ca, and of the second bed with Na and K. A suitable auxiliary regenerant solution such as NaCl is sent through the rst bed in order to restore Na-ion therein in exchange for Ca. The condition of the bed, as shown in Fig. 5, is an intermediate'one and designated as C22. That is to say, the upperportion e of the bed in that condition is regenerated with Na-ion, while the lower portion still contains the previously adsorbed Caion. The spent liquor :lowing from this bed contains CaC12 as a result of the exchange of Na for Ca. The intermediate condition in the regeneration phase of the second stage or exchanger bed in Fig. 5 is designated as C24. H2804 is the regenerant solution whereby H-ionl are being restored in the exchanger by way of the H-ion cycle. In this condition the upper portion g of the bed is shown to have been regenerated with H-ion, while the lower portion h still contains the previously adsorbed Na and K-ion.

The spent regenerant liquor iiowing from this bed contains Na2SO4 and K2SO4 as a result of the exchange. After the auxiliary regeneration of the rst bed with NaCl, and the H-cycle regeneration with HQSO. of the second bed have been completed, these beds are then in a condition to be re-used in the saturation phase, that is, in the treatment of the juice, an intermediate condition of which phase is shown in Fig. 4.

We claim:

l. vIn the ion exchange treatment of sugarbearing solution containing Ca-ions adapted to form with H2504 regenerant solution precipitable reaction products, and also containing cations adapted to form with H2804 soluble reaction products, in which the solution is passed through a bed of organic granular cation exchanger material operating in the H-ion exchange cycle and regenerable with H2804 regenerant solution, the method for minimizing Ca-sulfate coating forming in situ on such exchanger granules, which comprises the steps of conditioning the sugarbearing solution prior to its treatment in the H-l ion exchange material to eiect removal of ,said Ca-ions by passing the solution through a bed o'f cation exchanger material whereby the bed is saturated with Ca-ions from the solution in exchange for non-precipitable cations going into the solution, regenerating said bed with an auxiliary regenerant solution containing in suitable molar concentration non-precipitable cations to exchange with the preclpitable cations in the bed whereby there is discharged from the bed spent regenerant liquor containing said precipitable cations.

2. The method according to claim 1, in which the auxiliary regenerant solution comprises at least one of the alkali metal salts.

3. The method according to claim 1, in which the auxiliary regenerant solution comprises a sodium salt.

FRANKLIN N. RAWLINGS.

LOUIS un GEORG?. 

